**6.2 Liquid digestate for hydroponic baby leaf lettuce (***Lactuca sativa* **L.) cultivation**

Ronga et al. [67] evaluated the effect of liquid digestate on the production of "baby" lettuce under hydroponic system over three cycles. This digestate was the product of anaerobic digestion of a mixture of corn, triticale, liquid dairy manure, and grape stems.

In the first and second cycle, the combination of perlite with standard nutrient solution (SNE), perlite with liquid digestate, solid digestate with SNE, solid digestate with liquid digestate, and soil control with SNE was evaluated. In the third cycle, the combinations were peat with SNE, peat with liquid digestate, pelletized digestate with SNE, and pelletized digestate with liquid digestate.

Chemical analyses showed that the liquid digestate contained 17% organic carbon, 0.34% nitrogen, and 0.95% potassium (K2O) and has an electrical conductivity of 1.07 dS m<sup>−</sup><sup>1</sup> and a pH of 8.03, in addition to having the highest number of colony-forming units of all materials used (substrates and fertilizer materials) with 7.3 e+05 CFUs g<sup>−</sup><sup>1</sup> .

In the first cycle, treatments formed by the combination of solid digestate with SNE and perlite with liquid digestate produced higher dry weight of leaves, while the dry weight of root and total dry weight was benefited by the combination of perlite and digestate liquid. In addition, such treatment ensured the health of the crop by not finding coliforms in the plants.


**87**

of the variables.

**Figure 6.**

treatment replicate.

nutraceutical quality.

*Nutritive Solutions Formulated from Organic Fertilizers DOI: http://dx.doi.org/10.5772/intechopen.89955*

In the second cycle, as in the previous cycle, the combination of solid digestate with SNE and perlite with liquid digestate produced greater dry weight of leaves. The same trend of the abovementioned variable was presented in the rest

*Results of nutritious solution of hen, bovine, and chemical fertilizers: (a) yield by fruit cutting and average;* 

Based on the results shown, the authors consider the use of digestate for hydro-

In the third cycle, the use of liquid digestate only equaled the SNE in the harvest index when the substrate was peat, while when the substrate was pelletized

ponic production of lettuce to be a potential resource considering its low cost, environmental sustainability, agronomic interest, and microbial parameters.

The aim of the current study was to evaluate the nutraceutical quality of cantaloupe melon fruits fertilized with different organic fertilizer solutions (Preciado et al. (2015)); applied fertilization treatments consisted of an inorganic nutrient solution, compost tea, and vermicompost tea and leachate (leachate collected from vermicompost production) (**Figure 7**). The inorganic nutrient solution was prepared using highly soluble commercial fertilizers. The fertilizer

tap water to avoid phytotoxicity. The treatments were established in a completely randomized design using 10 plants per treatment, with each plant representing a

The main conclusions of the present study are as follows. The applied nutrient solutions (compost tea, vermicompost tea and leachate, and inorganic Steiner solution) affected the nutraceutical quality of melon, as the fruits produced using the organic solutions exhibited higher antioxidant capacity and phenolic content than the chemically fertilized melons (**Figure 8**). It is feasible to recommend the application of vermicompost nutrient solutions (leachate and tea) as fertilizer alternatives for the production of hydroponic cantaloupe melon with an improved

via dilution with

digestate, the liquid digestate produced higher plant height.

*(b) brix grades; (c) total phenols; and (d) antioxidant capacity.*

**6.3 Nutraceutical quality of cantaloupe melon fruits**

solutions were adjusted to a pH of 5.5 and an EC of 2.0 dS m<sup>−</sup><sup>1</sup>

#### **Table 4.**

*N, P, and K composition of the treatments (mg L<sup>−</sup><sup>1</sup> ).* *Nutritive Solutions Formulated from Organic Fertilizers DOI: http://dx.doi.org/10.5772/intechopen.89955*

#### **Figure 6.**

*Urban Horticulture - Necessity of the Future*

matter) and the hen the Meyfer brand, which has OMRI registration (37.7% organic matter). The extracts were prepared with a part compost and two water; the concentrate obtained was diluted with water until the indicated electrical conductivity and adjustment of pH to 6 with citric acid were obtained. The treatment of high-

The experiment was established in pots of 13 L capacity black plastic bags, and as a substrate was used, river sand (0.5–2 mm), previously sterilized. The genotype used was of habit determined variety "Caloro". The nutrient contents of the applied solutions, pH and EC, are presented in **Table 4**. All treatments had an average drainage of 20%. At 80 and 90–100 days after transplantation, the fruits with which

The results indicate that treatments with organic solutions (hen and bovine extract) achieved production, quality in Brix grades, and phenol content statistically equal to those obtained in fertilizer, fertilizing treatments such as synthetic chemicals, regardless of the electrical conductivity of nutrient solutions (**Figure 6**). However, the antioxidant capacity was significantly higher in organic nutrient solu-

solubility synthetic chemical fertilizers used the Steiner solution.

(p < 0.05).

digestate with SNE, and pelletized digestate with liquid digestate.

**Steiner solution**

crop by not finding coliforms in the plants.

**solution**

*N, P, and K composition of the treatments (mg L<sup>−</sup><sup>1</sup>*

**Nutrient Steiner** 

**6.2 Liquid digestate for hydroponic baby leaf lettuce (***Lactuca sativa* **L.)** 

Ronga et al. [67] evaluated the effect of liquid digestate on the production of "baby" lettuce under hydroponic system over three cycles. This digestate was the product of anaerobic digestion of a mixture of corn, triticale, liquid dairy manure,

In the first and second cycle, the combination of perlite with standard nutrient solution (SNE), perlite with liquid digestate, solid digestate with SNE, solid digestate with liquid digestate, and soil control with SNE was evaluated. In the third cycle, the combinations were peat with SNE, peat with liquid digestate, pelletized

Chemical analyses showed that the liquid digestate contained 17% organic carbon, 0.34% nitrogen, and 0.95% potassium (K2O) and has an electrical conductivity of 1.07

In the first cycle, treatments formed by the combination of solid digestate with SNE and perlite with liquid digestate produced higher dry weight of leaves, while the dry weight of root and total dry weight was benefited by the combination of perlite and digestate liquid. In addition, such treatment ensured the health of the

> **Chicken manure tea**

**dS m<sup>−</sup><sup>1</sup>** N 115 153 39.2 49 28.45 35.56 P 23 31 9.2 11.5 8.15 10.18 K 207 277 107 133.75 103 128.75

*).*

**Chicken manure tea**

**1.5 2 1.5 2 1.5 2**

**Bovine compost tea**

 and a pH of 8.03, in addition to having the highest number of colony-forming units of all materials used (substrates and fertilizer materials) with 7.3 e+05 CFUs g<sup>−</sup><sup>1</sup>

.

**Bovine compost tea**

the data were taken for evaluation were harvested.

tions with levels of 2 dS m<sup>−</sup><sup>1</sup>

**cultivation**

and grape stems.

dS m<sup>−</sup><sup>1</sup>

**86**

**Table 4.**

*Results of nutritious solution of hen, bovine, and chemical fertilizers: (a) yield by fruit cutting and average; (b) brix grades; (c) total phenols; and (d) antioxidant capacity.*

In the second cycle, as in the previous cycle, the combination of solid digestate with SNE and perlite with liquid digestate produced greater dry weight of leaves. The same trend of the abovementioned variable was presented in the rest of the variables.

In the third cycle, the use of liquid digestate only equaled the SNE in the harvest index when the substrate was peat, while when the substrate was pelletized digestate, the liquid digestate produced higher plant height.

Based on the results shown, the authors consider the use of digestate for hydroponic production of lettuce to be a potential resource considering its low cost, environmental sustainability, agronomic interest, and microbial parameters.

#### **6.3 Nutraceutical quality of cantaloupe melon fruits**

The aim of the current study was to evaluate the nutraceutical quality of cantaloupe melon fruits fertilized with different organic fertilizer solutions (Preciado et al. (2015)); applied fertilization treatments consisted of an inorganic nutrient solution, compost tea, and vermicompost tea and leachate (leachate collected from vermicompost production) (**Figure 7**). The inorganic nutrient solution was prepared using highly soluble commercial fertilizers. The fertilizer solutions were adjusted to a pH of 5.5 and an EC of 2.0 dS m<sup>−</sup><sup>1</sup> via dilution with tap water to avoid phytotoxicity. The treatments were established in a completely randomized design using 10 plants per treatment, with each plant representing a treatment replicate.

The main conclusions of the present study are as follows. The applied nutrient solutions (compost tea, vermicompost tea and leachate, and inorganic Steiner solution) affected the nutraceutical quality of melon, as the fruits produced using the organic solutions exhibited higher antioxidant capacity and phenolic content than the chemically fertilized melons (**Figure 8**). It is feasible to recommend the application of vermicompost nutrient solutions (leachate and tea) as fertilizer alternatives for the production of hydroponic cantaloupe melon with an improved nutraceutical quality.

**Figure 7.**

*Chemical composition of the nutrient solutions applied during the production of hydroponic cantaloupe melon in a greenhouse (Preciado et al., 2015).*

#### **Figure 8.**

*Total phenolic content (a and b) and antioxidant capacity (c) of hydroponic cantaloupe melon fruits produced using different nutrient solutions.*

#### **6.4 Hydroponic green fodder**

Salas et al. (2012) conducted a trial with the aim of evaluating the effect of organic nutrient solutions on yield, nutritional composition, total phenolic compounds, and in vitro antioxidant capacity of hydroponic green corn fodder produced in a greenhouse.

The treatments were vermicompost tea (TVC), compost tea (TC), and chemical solution (SQ ) as a control and were applied from day 5 until harvest day. The concentration of nutrients in the treatments used is shown in **Figure 9**. Treatments were applied twice daily (8:00 and 19:00) on the aerial part of the fodder, with an average volume of 4.63 L<sup>−</sup><sup>1</sup> m<sup>−</sup><sup>2</sup> day<sup>−</sup><sup>1</sup> .

**89**

**Figure 10.**

*Yield results and chemical composition of green fodder.*

**Figure 9.**

*Nutritive Solutions Formulated from Organic Fertilizers DOI: http://dx.doi.org/10.5772/intechopen.89955*

*Chemical composition of nutrient solutions applied in green fodder.*

The yield, content of total phenolic compounds, and antioxidant capacity of the hydroponic green maize forage obtained were similar in organic and chemical fertilization treatments. Also, although differences in dry matter and protein content were found, all nutritional parameters evaluated were within the values reported as acceptable in good nutritional quality fodder (**Figures 10a–c** and **11**). On the other hand, the total phenolic content of organic and inorganically fertilized FVH was less than 1% dry base, so the consumption of such fodder does not pose health risks to livestock related to the consumption of these compounds. Therefore, it is advisable to use organic fertilization solutions in the production of fVH of maize in greenhouse, due to the advantages that such solutions would represent from the

#### **Figure 9.**

*Urban Horticulture - Necessity of the Future*

**88**

**Figure 8.**

**Figure 7.**

*in a greenhouse (Preciado et al., 2015).*

**6.4 Hydroponic green fodder**

*using different nutrient solutions.*

duced in a greenhouse.

average volume of 4.63 L<sup>−</sup><sup>1</sup>

m<sup>−</sup><sup>2</sup>

 day<sup>−</sup><sup>1</sup> .

Salas et al. (2012) conducted a trial with the aim of evaluating the effect of organic nutrient solutions on yield, nutritional composition, total phenolic compounds, and in vitro antioxidant capacity of hydroponic green corn fodder pro-

*Total phenolic content (a and b) and antioxidant capacity (c) of hydroponic cantaloupe melon fruits produced* 

*Chemical composition of the nutrient solutions applied during the production of hydroponic cantaloupe melon* 

The treatments were vermicompost tea (TVC), compost tea (TC), and chemical solution (SQ ) as a control and were applied from day 5 until harvest day. The concentration of nutrients in the treatments used is shown in **Figure 9**. Treatments were applied twice daily (8:00 and 19:00) on the aerial part of the fodder, with an

The yield, content of total phenolic compounds, and antioxidant capacity of the hydroponic green maize forage obtained were similar in organic and chemical fertilization treatments. Also, although differences in dry matter and protein content were found, all nutritional parameters evaluated were within the values reported as acceptable in good nutritional quality fodder (**Figures 10a–c** and **11**). On the other hand, the total phenolic content of organic and inorganically fertilized FVH was less than 1% dry base, so the consumption of such fodder does not pose health risks to livestock related to the consumption of these compounds. Therefore, it is advisable to use organic fertilization solutions in the production of fVH of maize in greenhouse, due to the advantages that such solutions would represent from the

**Figure 10.** *Yield results and chemical composition of green fodder.*

#### *Urban Horticulture - Necessity of the Future*

**Figure 11.**

*Phenolic content and antioxidant content in green fodder.*

point of view of sustainability by the use of available resources. It is recommended for future studies to evaluate the in vivo antioxidant properties of hydroponic green forage produced under organic fertilization as well as the identification of phenolic compounds contained in this type of fodder.

## **7. Conclusions**

Organic fertilizers can provide essential nutrients soluble to plants, so as to be used in hydroponic systems in its various forms. Nutrient solutions can be formulated when soluble nutrients are extracted from the solid phase of organic manure, for this is essential to ensure that the organic materials used are harmless.

With these solutions it is possible to produce some vegetables without supplementing with other sources of nutrients (baby lettuce, chard, spinach, etc.). However, the solutions must be supplemented if solanaceas, cucurbits, or others plant groups are cultivated.

With organic solutions it is possible to have, in some vegetables, yields and commercial quality similar to solutions with chemical fertilizers. These vegetables also generally contain greater antioxidant capacity. The presence of other substances, in organic solutions, such as humic acids, phytohormones, and microorganisms, is responsible for the positive effects that have been obtained.

The nutritious solution, formulated from organic fertilizers, is not only an alternative for the nutrition of agricultural crops, but it also represents a more efficient way to use these resources.

## **Author details**

Juan Carlos Rodríguez Ortiz Facultad de Agronomía y Veterinaria UASLP, Mexico

\*Address all correspondence to: juancarlos.rodriguez@uaslp.mx

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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*Nutritive Solutions Formulated from Organic Fertilizers DOI: http://dx.doi.org/10.5772/intechopen.89955*

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